How to Repair a Boat Hull
Repairing a damaged boat hull can be fairly simple or extremely difficult, depending on the degree of damage to the hull, as well as the hull composition (i.e. wood, fiberglass, aluminum). Most modern boats are made of fiberglass, and the majority of damage sustained to them are minor cracks and chips. Larger repair jobs should almost universally be done by a professional.
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Things You'll Need
- Gel coat repair kit (available in marine stores)
- A piece of gel coat from your boat (if available)
- One sheet each of 150-, 220-, 400-, and 600-grain sandpaper
- Spray bottle or wet sponge
- Plastic spreader or plumber's knife
- "Zipper" kitchen bags
- Masking tape
- Rubbing compound
- Hull wax
Instructions
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1
Purchase the appropriate gel coat repair kit. Bring the chip from your boat to your marine store to properly color match your gel coat with the available pastes. If you cannot bring a chip, then make your best guess as to the color of your boat's hull. Unless the color is unusual, most marine stores will carry the necessary supplies. If your boat is an unusual color, you may have to obtain a gel coat repair kit from the manufacturer.
Some gel coat repair kits contain two tubes of material: the filler and the hardener. These compounds function much like an epoxy kit and must be properly mixed to be effective.
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2
Wet sand the damaged area. Dampen the cracked or broken area with a spray bottle or damp sponge, and gently sand the affected area with the 150-grain paper. Do not sand too vigorously or go far beyond the actual size of the crack/break. Be sure to re-wet the area as you sand it. When you are done sanding, the cracked edges should be smooth.
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3
Apply the gel coat. Fill in the cracked or broken area on the hull, and gently smooth it out with your plastic spreader or plumbers knife. Cover the repaired portion with a section of a kitchen "zipper" bag, and tape down the sides of the bag. This must be done because gel coat will not fully harden in open air and must be in a sealed environment.
Once the gel coat is dry, if the affected hull portion shows a "divot" in the coat, repeat Steps 2 and 3 until the final dried coat is flush with the hull.
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4
Wet sand again. Start using a 220-grain sandpaper, then move to 400-grain, and finally 600-grain. You might want to use a sanding block to keep the strokes even, but do not use a power sander.
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5
Buff and wax. Once you have finished sanding, apply the rubbing compound to give the area a glossy appearance. This may take several applications. Finally, when the hull achieves a glossy sheen, apply no less than three coats of hull wax to the newly repaired section. If your color match is good, and the repair is flush, the former damage should be nearly undetectable.
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Tips & Warnings
For simplicity's sake, choose a "premixed" gel coat kit that has both of the compounds in one tube.
If you have a hull puncture, it is best to leave the repair to professionals. While more expensive, a professional fiberglass worker will have the necessary tools to relay and intertwine the new glass, as well as the protective gear necessary for safe application.
